Flow over Broad Crested Weirs： Comparison of 2D and 3D Models

The flow over broad-crested weirs was simulated by computational fluid dynamic model. The water surface profile over broad crested weir was measured in a laboratory model and validated using two and three dimensional Fluent programs. The Reynolds Averaged Navier-Stokes equations coupled with the turbulent standard （k-ε） model and volume of fluid method were applied to estimate the water surface profile. The results of numerical model were compared with experimental results to evaluate the ability of model in describing the behaviour of water surface profile over the weir. The results indicated that the 3D required more time in comparison with 2D results and the flow over weir changed from subcritical flow at the upstream （U/S） face of weir to critical flow over the crest and to supercritical flow at downstream （D/S）. A reasonable agreement was noticed between numerical results and experimental observations with mean error less than 2 %.